The present invention relates to an RC calibration circuit and method thereof, and more particularly to an RC calibration circuit that utilizes an amplifier to generate a charging current under a charging mode and utilizes the amplifier to operate as a comparator under a comparing mode, and a method thereof.
When a passive element, such as a resistor or a capacitor, is fabricated in an integrated circuit, the variation of semiconductor processing may seriously affect the accuracy of the electrical characteristic of the passive element. For the example of a filter comprising a resistor and capacitor, a corner frequency as well as time constant of the filter is determined by the resistance of the resistor and the capacitance of the capacitor. When process variation occurs, the corner frequency of the filter is varied. As a result, the frequency band of the filter may deviate from the required band of the circuit system, and consequently affect the efficiency of the circuit system. To overcome the above-mentioned problem, a calibration mechanism can be built in the integrated circuit to calibrate the resistance of the resistor or the capacitance of the capacitor fabricated in the integrated circuit. The conventional calibration mechanism, however, may also greatly increase the area of the integrated circuit as well as the cost. Therefore, providing an efficient and low cost calibration mechanism to calibrate the resistor and the capacitor in the integrated circuit is a significant concern in the circuit design field.